The present invention relates to a safety valve for use in well bore operations. In particular, but not exclusively, the present invention relates to a safety valve for use in wellbore production tubing, for example, in cooperation with a progressive cavity pump or rodpump.
In the field of oil and gas drilling and well production, safety valves are commonly used in producing wells to prevent and contain accidents. For example, if downhole pressure exceeds a certain level, it is often a matter of urgency to shut in the well to prevent blowout and/or damage to equipment.
Less than a quarter of producing oil wells flow naturally. Therefore it is necessary to employ some means of artificial lift, for example a pump of some description. Such artificial lift means are also employed in subsea operations and in difficult locations in order to boost production.
Progressive cavity pumps (PCP) are generally employed in low flowrate applications where there is not enough lift to cause problems. Progressive cavity pumps are flexible and reliable, and in general resistant to abrasive solids. In comparison to some other pumping methods the PCP produces an almost fluctuation-free flow out of a well. PCPs are also durable and less prone to damage than, for example, ESP pumps.
However, in subsea drilling and the majority of offshore operations there is a strict requirement for failsafe safety systems to be employed. These failsafe systems are often safety valves that can be closed automatically in the event of a problem.
A typical safety valve employed in the art is a flapper valve. This kind of valve is biased closed in general by a spring which forces the flapper upwards against a sealing surface. Typically an actuation means such as a rod or a sleeve is provided, and is controlled by a hydraulic line from surface which, when actuated, moves the flapper to an open position. Removal of pressure will cause the flapper to close again.
This kind of safety valve is useful for shutting in a well when there is a problem occurring downhole. However, such flapper valves are unsuitable for progressive cavity pumps, where a conduit in the form of a rod string is required to pass through the bore of the system down to the PCP rotor. The PCP is typically located below what would be the location of a failsafe valve.
One solution in the art is to use a rod string with a modified end which pushes open the flapper valve and continues moving downwards to mate with the PCP rotor or a further rod string connected to the PCP rotor. Should a problem occur downhole the rod can be pulled, disengaging from the rotor and, once clear of the flapper, the safety valve can be closed. However, as discussed above, it is clear that should a problem occur at the surface and the rod cannot be pulled then the valve will remain open.
There is little provision for failsafe valves that allow PCPs or rod pumps to be driven therethrough, while maintaining a valve that can be actuated regardless of whether the problem is downhole or at the surface. Furthermore there is little provision for failsafe valves that allow the valve to be opened or closed irrespective of whether the rod is inserted or retracted, or conversely that allow PCPs to be driven therethrough regardless of whether the valve is open or closed.
These problems and disadvantages apply equally in relation to use of safety valves with other downhole equipment such as drill strings, artificial lift equipment such as gas lift pipes, and electrical/fibre-optic/hydraulic penetrators. For example, a rotary drill string suffers from similar disadvantages in terms of an inability of prior safety valves to facilitate drive transfer through the valve whilst maintaining the ability to quickly close the valve. In the case of gas lift pipes and penetrators, whilst it is not necessary in these cases to transfer drive through the valve, the problem of requiring the gas lift/penetrator string to be pulled to close the safety valve remains.
It is an object of at least one embodiment of the present invention to provide a safety valve that obviates OR mitigates at least one limitation of the prior art.
According to a first aspect of the present invention, there is provided a safety valve for use with upper and lower conduits located in wellbore production tubing, the safety valve comprising:
a housing having a longitudinal bore extending therethrough;
a coupling member for coupling the upper conduit to the lower conduit, the coupling member sealably mounted within the longitudinal bore;
an annular flow passage bypassing the coupling member; and
valve means located in the annular flow passage.
Preferably, the upper conduit is an upper tubing string and the lower conduit is a lower tubing string. The tubing strings may provide a mechanical support and/or may define a fluid flow path to enable a downhole operation to be conducted.
The coupling member may serve for fluidly coupling the upper conduit to the lower conduit, to permit fluid flow therebetween. This may facilitate use of the safety valve with gas lift tubing or pipe comprised of upper and lower conduits in the form of upper and lower tubing strings, where an upper gas lift tubing section is to be coupled to a lower gas lift tubing section. This may enable injection of gas into the production tubing below the valve (in an artificial, gas-lift procedure), whereby recovery of well fluids is stimulated, the well fluids flowing through the annular flow passage into the production tubing above the valve and to surface.
The coupling member may be adapted to be connected to one of the upper and lower conduits, and the housing may be adapted to be connected to the other one of the upper and lower conduits. Accordingly, by sealingly mounting the coupling member in the housing bore, the upper and lower tubing strings may be fluidly coupled, and the connecting member may therefore serve for indirectly connecting the upper and lower tubing strings together.
Alternatively, the coupling member may serve for connecting the upper and lower conduits together, and may therefore serve for directly connecting the conduits.
The coupling member may comprise a tubing section, pipe, sub or the like which may serve for coupling the upper and lower conduits and may therefore be adapted to form part of a completed conduit extending through the valves.
The coupling member may take the form of a penetrator body, the penetrator body serving for coupling the upper and lower conduits which may be upper and lower penetrator conduits. The upper and lower penetrator conduits may comprise or take the form of tubes, pipes, wires and/or cables and may be electrical, fibre-optic and/or hydraulic tubes, pipes, wires or cables and may serve for providing power and/or control signals to downhole equipment, particularly pumps such as electrical submersible pumps (ESPs). Accordingly, when the upper and lower conduits are coupled, supply of power and/or control signs to downhole equipment may be facilitated. Additionally, by sealably mounting the penetrator body in the housing bore, return flow of fluid (such as well fluids lifted by the pump) may be directed along the flow passage whilst the body provides connection between the upper and lower penetrator conduits.
Preferably however, the coupling member takes the form of a motion transferring member arranged to provide a means to provide motion from the upper conduit to the lower conduit. The safety valve may be for use with upper and lower conduits in the form of upper and lower tubing strings, which may be upper and lower rod strings of a pump. Alternatively, the safety valve may be for use with upper and lower conduits in the form of upper and lower tubing strings which may be respective sections of a drill string, or any other downhole tubing of a type where motion is to be transferred through the safety valve.
According to a second aspect of the present invention there is provided a safety valve for use with upper and lower rod strings in production tubing when located within a well bore, the safety valve comprising a substantially cylindrical housing with a longitudinal bore therethrough, the cylindrical housing containing a motion transferring member, the motion transferring member sealably mounted within the longitudinal bore but arranged so as to provide a means to transfer motion from the upper rod string to the lower rod string, and an annular flow passage bypassing said motion transferring member, the annular flow passage having valve means located therein.
The annular flow path and valve means therein provides a fluid path which can be opened and closed to regulate flow in a production string. The motion transferring member provides a means of transferring motion from above the safety valve to below the safety valve without compromising the effectiveness of the valve means.
Most preferably and advantageously the valve means is an annular valve. Annular valves are well known in the art and are very effective in shutting off producing wells. Such a valve would allow the motion transferring member to move within the housing whether the valve was open or closed.
Preferably the coupling/motion transferring member comprises a hollow, substantially cylindrical body. Preferably the motion transferring member forms a sealtight fit within the longitudinal bore.
Preferably the annular flow passage divides a substantial portion of the housing into an outer cylindrical housing and an inner cylindrical housing.
The annular cavity allows the fluid to bypass the coupling/motion transferring member, and the annular valve located therein opens or closes to allow or prevent fluid flow up the production tubing.
Preferably the annular valve comprises a hollow cylindrical valve sleeve surrounding a hollow cylindrical valve body. Preferably the cylindrical valve body is an integral part of the inner cylindrical housing. Preferably the valve sleeve is movable along the valve body. Preferably the valve sleeve has one or more valve sleeve apertures. Preferably the valve body has one or more valve body apertures. The valve is open when the valve sleeve moves to a position where the sleeve apertures align with the valve body apertures.
Most preferably the annular valve has an actuation means which displaces the valve sleeve of the annular valve. This actuation means therefore controls the opening and closing of the valve, allowing and preventing fluid flow within the tubing.
Preferably the actuation means for the annular safety valve is a rod piston. Preferably the rod piston is located in a longitudinally extending rod piston cavity.
Preferably the rod piston is axially moveable within the rod piston cavity. Preferably movement of the rod piston is effected by means of hydraulic fluid pressure within the rod piston cavity.
Preferably the rod piston is biased with a spring. In this way the piston, and hence the valve can be biased to be default open or default closed.
Preferably the rod piston cavity is in fluid communication with a hydraulic control line port located at an outer surface of the substantially cylindrical housing. Preferably the hydraulic control line port connects to a control line. Preferably the control line extends to the top of the wellbore. This will allow the annular valve to be opened or closed from the surface by controlling hydraulic fluid pressure in the control line.
Optionally there is an intermediary stage between the hydraulic control line port and the control line. Preferably the intermediary stage is a component of a downhole fixture located in the wellbore. In particular embodiments, the safety valve may be adapted to be located in an existing downhole valve. Accordingly, the downhole fixture may be a sub-surface safety valve (SSSV) and may be locked open. The SSSV may take the form of a tubing retrievable surface controlled safety valve (TRSCSV). In this way, the control line of an existing, already installed, downhole component can be employed to actuate the safety valve of the present invention. In these embodiments, the safety valve of the invention may be adapted to engage within a main bore of the existing valve, which may be locked open by the safety valve or using the existing valve control equipment.
Preferably the movement of the motion transferring member is restricted to rotational motion. This facilitates the transfer of rotational motion from an upper rod string to a lower rod string, allowing for example a progressive cavity pump to be driven from the surface, or transfer of motion between upper and lower drill strings or other rotatable tubing strings.
Alternatively the movement of the motion transferring member is restricted to axial motion. This alternative allows the transfer of an axial reciprocation of the upper rod string to the lower rod string, allowing for example a rod pump to be driven from the surface.
Preferably sealing means are provided between the coupling/motion transferring member and the housing. This ensures that any fluid flow is either prevented or directed through the annular flow passage, depending on whether the annular valve is closed or open, respectively.
The sealing means maybe a plurality of circumferentially extending seals. The circumferentially extending seals maybe located within circumferentially extending recesses on an outer surface of the coupling/motion transferring member. Alternatively the circumferentially extending seals are located within circumferentially extending recesses on an inner surface of the longitudinal bore.
Preferably a bearing means is provided between the coupling/motion transferring member and the substantially cylindrical housing. This bearing means reduces friction between the motion transferring member and the housing.
The valve may comprise means for connecting the coupling/motion, transferring member to the upper conduit which may comprise a female receptacle integral to the coupling/motion transferring member and a male insert provided on or adapted to be coupled to the upper conduit.
The male insert may comprise a spline shaft, and the female receptacle may comprise a spline sleeve into which the spline shaft forms an interference fit. The spline shaft and spline sleeve mate to form a connection capable of transferring rotational motion.
Preferably the male insert further comprises a locking mechanism. The locking mechanism is to hold the spline shaft within the spline sleeve and prevent unwanted retraction of the upper conduit.
The locking mechanism may comprise a key. The female receptacle may comprise a recess with which the key can communicate. As the upper conduit with the male insert is lowered into the safety valve, the key locates within the recess and prevents the upper conduit from being forced upwards.
Preferably the male insert further comprises a non-rotating mandrel. Preferably the locking mechanism is an integral part of the non-rotating mandrel. Most preferably and advantageously the upper conduit is free to rotate within the non-rotating mandrel. This means that the locking mechanism does not rotate, and only the upper conduit rotates, making the locking mechanism more effective.
Preferably the male insert further comprises a no-go key. Most preferably the no-go key is fixed in location on the non-rotating mandrel. Preferably the female receptacle further comprises a shoulder with which the no-go key communicates. The no-go key and the shoulder contact to stop the upper conduit travelling too far downwards.
The valve may comprise means for connecting the coupling/motion transferring member to the lower conduit, which may comprise a female receptacle integral to the coupling/motion transferring member and a male insert provided on or adapted to be coupled to the top end of the lower conduit.
Optionally the lower conduit is a lower rod string and may be a PCP rotor.
Preferably the top end and the bottom end of the housing are adapted for connection to production tubing.
Optionally, the means of connecting the coupling/motion transferring member to the lower conduit further comprises a torque reducing means. A PCP rotor in rotation often results in a transfer of torque to the rod string driving the rotation. This creates a backlash rotation wherein the rod string moves in a circular path within the bore. A torque reducing means would reduce the transfer of this torque into the safety valve.
Whilst the above aspects of the invention have been defined in relation to a safety valve for use with tubing strings located in wellbore production tubing, it will be understood that the safety valve may be utilised in any desired, suitable downhole tubing such as casing, liner or the like. Equally, it will be understood that the safety valve may be for use with any suitable upper and lower tubing strings. The safety valve may also have uses in other types of tubing such as pipelines.
Further features of the present invention are defined in the claims.